As is known, the motor vehicle manufacturers demand that the cooling circuit filling pipes should withstand displacements in all three directions as well as vibrations, which is obtained by the presence of undulations or corrugations defining reliefs and hollows on the outer face of these pipes, which are conventionally made of rubber for reasons of flexibility in response to the displacements, and of resistance to the fluid conveyed and to its temperature and circulation pressure.
Recently, and in particular for economic reasons, research has been conducted into producing such corrugated pipes using thermoplastic materials for its regions that are fixed in relation to the displacements, while retaining rubber for the regions subject to these displacements, or even entirely of one or more thermoplastic materials in order to further reduce their cost of manufacture.
The document U.S. Pat. No. 6,021,816 can, for example, be cited for the description of such a corrugated pipe which is entirely thermoplastic, whose ring-shaped reliefs have overall rounded contours of elliptical, oval or circular type, with angular offsets between these reliefs.
A major drawback in the known corrugated thermoplastic pipes lies in these rounded geometries for the contours of these annular reliefs which, if they favour the flexibility of the pipe for its displacements, have the undesirable effect of resulting in a flattening and therefore an elongation of these reliefs in the axial direction of the pipe, because of the high operating temperatures and/or pressures.